Article: Ratio of Forced Expiratory Volume in 1 second /Slow Vital Capacity (FEV 1/SVC)<0.7 is associated with clinical, functional, and radiologic features of obstructive lung disease in smokers with preserved lung function
Authors: Spyridon Fortis, Alejandro Comellas, Surya P Bhatt, Eric A Hoffman, MeiLan K Han, Nirav R Bhakta, Robert Paine 3rd, Bonnie Ronish, Richard E Kanner, Mark Dransfield, Daniel Hoesterey, Russell G Buhr, R Graham Barr, Brett Dolezal, Victor E Ortega, M Bradley Drummond, Mehrdad Arjomandi, Robert J Kaner, Victor Kim, Jeffrey L Curtis, Russell P Bowler, Fernando Martinez, Wassim W Labaki, Christopher B Cooper, Wanda K O’Neal, Gerald Criner, Nadia N Hansel, Jerry A Krishnan, Prescott Woodruff, David Couper, Donald Tashkin, Igor Barjaktarevic
Journal: Chest. 2021 Feb 1;S0012-3692(21)00229-4. doi: 10.1016/j.chest.2021.01.067. Online ahead of print.
Background: Mild expiratory flow limitation may not be recognized using traditional spirometric criteria based on the ratio of Forced Expiratory Volume in 1 second (FEV1) to Forced Vital Capacity (FVC).
Research question: Does slow vital capacity (SVC) instead of FVC increase the sensitivity of spirometry to identify patients with early or mild obstructive lung disease?
Study design and methods: We included 854 current and former smokers from the SPIROMICS cohort with a post-bronchodilator FEV1/FVC≥0.7 and FEV1%predicted≥80% at enrollment. We compared baseline characteristics, chest CT features, exacerbations, and progression to COPD (post-bronchodilator FEV1/FVC<0.7) during the follow-up period between 734 participants with post-bronchodilator FEV1/SVC≥0.7 and 120 with post-bronchodilator FEV1/SVC<0.7 at the enrollment. We performed multivariable linear and logistic regression models, negative binomial and interval-censored proportion hazards regression models adjusted for demographics and smoking exposure to examine the association of FEV1/SVC<0.7 with those characteristics and outcomes.
Results: Participants with FEV1/SVC<0.7 were older, had lower FEV1 and more emphysema than those with FEV1/SVC≥0.7. In adjusted analysis, individuals with post-bronchodilator FEV1/SVC<0.7 had greater %emphysema by 0.45% (95%CI=0.09-0.82), % gas trapping by 2.52% (95%CI=0.59-4.44), and %functional small airways disease based on parametric response mapping (PRMfSAD) by 2.78%(95%CI = 0.72-4.83) at baseline than those with FEV1/SVC≥0.7. During a median follow-up time of 1500 days, FEV1/SVC<0.7 was not associated with total exacerbations (IRR=1.61;95%CI=0.97-2.64) but was associated with severe exacerbations (IRR=2.60;95%CI=1.04-4.89). FEV1/SVC<0.7 was associated with progression to COPD during a 3-year follow-up even after adjustment for demographics and smoking exposure (HR=3.93;95%CI=2.71-5.72). We found similar results when we examined the association of pre-bronchodilator FEV1/SVC<0.7 or FEV1/SVC<LLN with chest CT features, and progression to COPD.
Interpretation: Low FEV1/SVC in current and former smokers with normal spirometry can identify individuals with CT features of COPD and at risk for severe exacerbations, and is associated with progression to COPD in the future.
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